1. Field of the Invention
The present invention relates to a cleaning device for cleaning residual toner from the surface of a photosensitive member in an image forming apparatus.
2. Description of the Related Art
Cleaning devices for cleaning residual toner from the surface of a photosensitive member in an image forming apparatus are well known which clean said residual toner from the surface of a photosensitive member by means of pressure contact of a cleaning blade with the surface of said photosensitive member. In cleaning devices of the aforesaid type, the modes of pressure contact of the cleaning blade with the surface of the photosensitive member include counter type modes wherein the angle formed between the cleaning blade and the uncleaned surface of the photosensitive member is an obtuse angle, and trailing type modes wherein said angle is an acute angle.
The cleaning efficiency of the aforesaid cleaning blades is generally determined by the characteristics of the material used to form the blade and the various conditions of pressure contact between the blade and the surface of the photosensitive member. Among the conditions of the aforesaid pressure contact, the most important conditions are the setting of the pressure contact force when the cleaning blade makes pressure contact with the photosensitive member, and the setting of the pressure contact angle. The pressure contact angle .theta. is the angle formed between the cleaning blade and the tangent plane of the photosensitive member.
Conventional cleaning blades are subject to certain disadvantages which occur due to changing environmental factors such as temperature and humidity and changes over time due to localized deformation of the blade and grip of said blade as a result of changes in the blade's Young's modulus which expresses blade hardness, said disadvantages including fluctuation in the amount of flexion .DELTA.u of the cleaning blade when said blade comes into pressure contact with the surface of the photosensitive member, thereby causing variation of the pressure contact angle .theta..
(The amount of flexion .DELTA.u of the cleaning blade is the amount of movement of corner edge P of cleaning blade 1 in pressure contact with the surface of the photosensitive member from an initial position which produces a flexion in said cleaning blade 1, as shown in FIG. 4.) Counter type cleaning blades have disadvantages such as filming and the like which result from retained toner and toner pressed against the surface of the photosensitive member when the pressure contact angle .theta. changes, and particularly when said angle increases. Trailing type cleaning blades also have disadvantages in addition to deterioration of cleaning efficiency similar to that occurring in counter type cleaning blades, such as noise generation resulting from rubbing against the photosensitive member.
Further disadvantages arise from differences in Young's modulus among individual blades during manufacturing of the cleaning blades, which causes differences in the amount of flexion .DELTA.u of individual cleaning blades, and results in a diverse range of cleaning efficiencies even among image forming apparatus of the same type.